Purpose: The study presented differentiates between the aetiological agents of bacterial keratitis in patients with and without a history of contact lens wear. Based on these results, recommendations are given for optimal antibiotic primary therapy.
Patients and methods: Swabs and corneal scrapings were taken from 218 patients referred to the University Eye Hospital in Munich with a diagnosis of bacterial keratitis from 1989 to 1997. Ninety-two of these patients had a history of contact lens wear; 126 had none. The germs were isolated and identified by staining and microscopy. Observing polymicrobial growth in 51 patients, a total of 275 germs was isolated.
Results: The most frequent pathogens were Staphylococcus epidermidis (44%), S. aureus (18%), Streptococcus spp. (10%), Propionibacterium acnes (7%) and Pseudomonas aeruginosa (6%). Gram-negative germs were nearly exclusively isolated from contact lens wearers, gram-positive germs were predominant in non-contact lens wearers.
Conclusion: Keratitis in patients with a history of contact lens wear is often caused by aggressive gram-negative germs. Those cases should immediately be treated with quinolones and erythromycin. In keratitis caused by gram-positive pathogens, a combination with aminoglycosides and erythromycin is sufficient.